Having a collision object. How to kill particles from a defined source?
You can let particles Die on Hit by enabling this feature for one of your P object.
Collision object with Kill Particles option can do the same, but there is not a possibility to restrict it for a specific particle system - it works globally.
Particle System Properties &gt; Physics &gt; Deflection &gt; Die on Hit


Or you can let collide particles with specific group of objects via Collision Collection.